Yarn storage and feed device

ABSTRACT

A yarn storage and feed device for textile machines, comprising a storage body defining a storage surface as well as a winding member for the yarn, the winding member and the storage member being adapted to be rotated relative to each other for transporting the yarn from a feed side of the device onto the storage surface of the storage member and for forming a yarn supply from which the yarn is removed towards the take-off side of the device, and further comprising yarn guide members, which are arranged in the yarn path from the feed area to the take-off area and which are provided with yarn guide surfaces coated with sintered ceramic material or consisting of sintered ceramic material, the yarn being deflected on the yarn guide surfaces at various angles. With regard to particularly advantageous frictional conditions, at least the yarn guide surface (L) having the largest deflection angle (180°-α) is made of a high-density sintered material containing mainly nitride, carbide and/or carbonitride hard materials. This sintered material is formed in an encapsulation in accordance with an isostatic hot-press sintering method for producing thus a yarn guide member.

DESCRIPTION

The present invention refers to a yarn storage and feed device.

In yarn storage and feed devices the yarn should be treated as gently aspossible along its yarn path through the device and it should besubjected to the smallest possible frictional loads when it comes intocontact with components of the device several times. Part of thecomponents of the device rotate relative to the running yarn, the yarnis carried along and deflected, or it circulates relative to stationarycomponents, it oscillates and is subjected to jerky acceleration anddeceleration and is moved between spaced guide surfaces in aballoon-forming manner. Yarn guide surfaces, which are coated withsintered ceramic material or which are made of said material, arenormally provided at the locations at which yarn contacting is to beexpected. Up to this day, conventional abrasion-proof sintered materialhas been used for this purpose. In spite of increasingly high yarnspeeds, e.g. 2,000 m/min and more, a more and more compact structuraldesign is aimed at in the case of modern yarn storage and feed devicesfor modern textile machines, e.g. jet weaving machines, so thatespecially the forces acting on the yarn along the yarn path becomeincreasingly important. The quality of a yarn storage and feed device isjudged on the basis of its reliability, i.e. the frequency of yarnbreaks in operation, since each yarn break will cause a standstill ofthe textile machine supplied and perhaps of additional systems followingsaid textile machine. Each standstill will result in a loss ofproduction causing high financial losses. Yarn breaks occurpredominantly between the feed area and the storage member of the yarnstorage and feed device, i.e. in an area where the yarn is normallysubjected to friction as well as to a deflection so that it is naturalto suspect that there is a connection between the yarn break frequencyand the yarn guide surfaces and the influence of the yarn guide surfaceson the yarn.

The object of the present invention is to provide a yarn storage andfeed device of the type mentioned at the beginning by means of which thefrequency of yarn breaks can be reduced.

In accordance with the present invention, there is provided a yarnstorage and feed device for textile machines, comprising a storage bodydefining a storage surface, a winding member for the yarn, the windingmember and the storage member being rotatable in relation to each otherfor transporting the yarn from a feed side of the device onto thestorage surface of the storage member and for forming a yarn supply fromwhich the yarn is removed towards the take-off side of the device, saiddevice further comprising yarn guide members which are arranged in theyarn path from the feed side to the take-off side and formed as moldingsand which comprise yarn guide surfaces coated with a ceramic sinteredmaterial or composed of a ceramic sintered material, the yarn beingdeflected on the yarn guide surfaces at various angles, at least theyarn guide surface having a large deflection angle being formed on ahigh-density sintered molding of hard material made by hot isostaticpressing in an encapsulation.

Surprisingly enough, the frequency of yarn breaks can be reduced byusing this sintered material at least in guide surfaces having a largeyarn deflection angle. The cause of this surprising improvement is,presumably, that the friction between the yarn and the guide surface issubstantially reduced due to the nature of the material used, and thisreduced friction will result in smaller mechanical loads on the yarn,and this will have a positive effect on the quality of the yarn storageand feed device especially in the case of higher yarn speeds.Surprisingly enough, it turns out that, in comparison with the frictioncaused by conventional sintered material, the friction will be reducedfor practically all types and qualities of yarn by the use of thepresent sintered material, i.e. although the frictions which can bemeasured in the case of a synthetic yarn as well as in the case of acotton yarn are nominally different, the frictions will in both cases belower than the friction caused by conventional sintered material.Another point of essential importance with regard to this low frictioncan be that the yarn guide member including the yarn guide surface isproduced in a very specific manner, viz. in accordance with an isostatichot-press sintering method in an encapsulation. This prerequisite is ofimportance separately as well as in combination with the selection ofthe hard material. The hard materials belonging to the group of elementsSi, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W (silicon, boron, titanium,zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,tungsten), in particular silicon and/or boron, provide the possibilityof achieving in the sintered material the sliding properties which areextremely advantageous with regard to the various yarns, also the smallgrain sizes (approx. 1 micron), which can be obtained in the case ofthese materials, being, presumably, very important with regard to thesesliding properties. The isostatic hot-press sintering process in acapsule prevents foreign substances or substances which woulddeteriorate the mechanical and thermal properties, respectively, frompenetrating into the raw material to be sintered. This, however, alsoinfluences the excellent sliding properties of the surface of the yarnguide surface.

Sintered material containing one of the above-mentioned hard materials,e.g. silicon nitride, as a main component is used in various fields oftechnology, but the decisive prerequisites for the use and for theselection of this extremely expensive sintered material are normallyhigh mechanical loads in combination with strong thermal loads(high-temperature range). This sintered material is, in high-densityquality, used e.g. for turbine blades, combustion space linings,nozzles, pump components, valve seats, cutting tool inserts, rollerelements for roller bearings, components for beater mills and the like.Cases of use with regard to which neither the high mechanical strengthnor the high temperature strength is of importance are not known inconnection with this sintered material.

In view of the fact that, for reasons of costs and because of themechanical loads acting on the yarn and varying in response to thedeflection angle and the length of the contact area, among otherfactors, a selection has to be made from the guide surfaces which maypossibly cause yarn breaks. When deflection angle is large, asubstantial yarn contact pressure has to be expected, which is ofimportance with regard to the degree of load to which the yarn will besubjected. In the case of this type of guide surfaces, the low frictionof the yarn is particularly important.

The main components of the sintered material are, in principle,components which are normally used with regard to special mechanicalloads and/or thermal loads. In a yarn guide surface, however, theextremely low friction, which is, in principle, of secondary importance,but which is extremely important with regard to yarns, is also obtainedbecause ceramic material has a small grain size and is of hard materialmolded in a high-density. This is, in principle, of benefit to thestrength of the material. Silicon nitride proved to be a particularlyuseful hard material in this respect. Minor additions of boron nitrideand/or boron carbide are advantageous. Yttrium oxide as an additiveprovides the possibility of achieving a high density and good adhesionof the components.

Although the yarn break frequency is reduced by the use of thehigh-density sintered ceramic material for the guide surfaces having alarge yarn deflection angle, e.g. an angle exceeding 90°, it will--inview of the fact that also the other guide surfaces in the yarn path maycause yarn breaks--still be expedient to produce several or all guidesurfaces from the high-density sintered material, which contains e.g.silicon nitride as a main component, since this will further reduce theprobability of yarn breaks which cannot be localized exactly.

The use of the isostatic hot-pressing method will result in a lowsurface friction.

An additional expedient embodiment is the case in which the storagemember has a cylindrical shape and includes a draw-off edge for theyarn, which serves as a yarn guide surface between the store of yarn andthe draw-off area of the device. Also this area of the device can be acritical zone with regard to yarn breaks, especially in cases in whichguide surfaces with extremely advantageous sliding properties arealready provided upstream and downstream of said area. Hence, it will beadvantageous to use in this area, too, the high-density sintered ceramicmaterial containing the above-mentioned hard materials, e.g. siliconnitride, as a main component.

Additional advantageous embodiments relate to the case in which thestorage member is arranged such that it stands still and in the case inwhich the winding member is a pipe member projecting from a hollow mainshaft, which is connected to a rotary drive means, radially outwards upto and beyond the storage surface of the neighbouring storage member,the free end of said pipe member having arranged therein the yarn guidemember including the guide surface which defines a large deflectionangle, e.g. a deflection angle exceeding 90°, for the yarn running fromthe main shaft to the storage surface. Within the groove nonvaryingadvantageous sliding conditions exist for the yarn. Also in the case ofunavoidable yarn migrating motions, which will occur when the yarn ismoving, the contacting length between the yarn and the guide surfacewill essentially always be the same. There are no sharp edges orprojections which might overstress the yarn locally. Optimum slidingconditions exist for the yarn also when said yarn arrives at and movesaway from the guide surface. The loads occurring during the yarndeflection process are uniformly distributed over the effective lengthof the guide surface and due to the low friction, in particular in casesin which silicon nitride is used as hard material main component, theyare kept low.

The above-mentioned uniform distribution of the small forces acting onthe yarn during the deflection process is specially guaranteed when theradius of curvature does not change.

In another important embodiment, the funnel-shaped trough permits theyarn to carry out a lateral migrating motion without coming into contactwith any abrasive edges and since the same yarn guide member can be usedfor both directions of rotation of the winding member.

Finally, there is an embodiment which is structurally simple and easy tomount. The cylindrical outer section serves to secure the yarn guidemember in position. The inner yarn guide surface provided with thecollar is responsible for the gentle treatment of the yarn, the yarncoming never into contact with the component of the device on which theyarn guide member is secured in position.

In the case of this type of use of this special sintered material, asecondary effect which is most welcome are the high abrasion resistanceand the high mechanical strength, since the yarn guide surfaces willthus not be subjected to any substantial wear even after a long servicelife and even in cases in which abrasive yarns are used, and since thestructural design of the yarn guide members can thus be gracile and,consequently, light, which will result in small inertia forces when saidyarn guide members are in motion.

Embodiments of the subject matter of the invention are explained on thebasis of the drawing, in which

FIG. 1 shows a schematic representation of the yarn path in a yarnstorage and feed device,

FIG. 2 shows a side view of a yarn storage and feed device, part of saidside view being shown in a longitudinal section, and

FIGS. 3a and 3b show associated views, partially in a sectional view, ofa yarn guide member of a type adapted to be used in FIGS. 1 and 2.

FIG. 1 schematically outlines a typical yarn path of a yarn Y through ayarn storage and feed device F in order to show how the yarn Y, which istransported in the direction of the arrows, passes several yarn guidesurfaces L, which are positioned one after the other in the yarn path,touches said guide surfaces in passing and is deflected whereupon itstransport is continued. For storing the yarn in a yarn supply 3consisting of several yarn windings, the yarn storage and feed device Fis provided with a storage member S, which has an e.g. cylindrical shapeand the outer circumference of which defines a storage surface 2. Facinga draw-off side A for the yarn, one end portion of the storage member Sis provided with a draw-off edge 4 across which the yarn is drawn offand simultaneously deflected. The axis of the device and of the storagemember S is provided with reference numeral 5. The yarn Y enters thedevice approximately in the direction of said axis and leaves the deviceat the draw-off side again close to said axis. At this location, a yarnguide surface L is provided within a yarn guide member 13, which isconstructed e.g. as a yarn eye and which is secured in position in aholding means 6 in a stationary manner. The yarn guide surfacepositioned at the feed side I is formed in a yarn guide member 8, whichis secured in position in a hollow main shaft 9 within the stationaryhousing 7. A rotary drive means, which is not shown, is connected to themain shaft 9. At the end of the main shaft 9, an additional yarn guidesurface L is provided in a yarn guide member 10, which is constructed asa yarn eye and which deflects the direction of movement of the yarn awayfrom the axis 5 at an oblique angle and radially outwards (deflectionangle 180°-β). The main shaft 9 has secured thereto a pipe member 11,which includes an angle β with the axis 5 and which is adapted to berotated together with said main shaft 9, said pipe member 11 projectingoutwards up to and beyond the storage surface 2 of the storage member Sand being there provided with an additional guide surface L within ayarn guide member 12. The pipe member 11 defines a winding member M, theyarn being drawn off a supply bobbin, which is not shown, and wound ontothe storage surface 2 in response to the rotation of said windingmember. At the draw-off side A, the yarn is acted upon by a draw-offforce, which removes the yarn from the yarn supply 3 as required. Therotational movement of the main shaft 9 and of the winding member Mtakes place e.g. in response to the size of the yarn supply 3, i.e. assoon as the yarn supply 3 (the number of windings) becomes smaller whenthe yarn is being removed, the winding member M will again wind yarnwindings onto the storage surface 2. Optionally, a yarn advancingmember, which is not shown, may be provided, said yarn advancing memberadvancing the yarn windings in the yarn supply in the direction of thedraw-off edge 4. As an alternative possibility, a structural designcould be provided in the case of which the storage member S comprisestwo interengaging cylindrical elements having eccentric axes of rotationwhich are oblique relative to each other for generating thus anadvancing motion for the yarn supply and for causing a separation of theyarn windings. These principles are sufficiently known.

The yarn guide surface L in the yarn guide member 12 defines for theyarn a deflection area having a large deflection angle (180°-α), whichis in the present case even larger than 90°, said deflection anglehaving a value between e.g. 175° and 120°, preferably between 150° and135°, in cases in which α is in the range from 15° to 60°, preferablybetween 30° and 40°. An additional factor determining the deflectionangle is the angle β between the axis 5 and the pipe member 11, saidangle β lying e.g. in the range between 45° and 60°. The yarn Y is notonly deflected in a radial plane--as shown in this sectional view--butit is additionally deflected in a direction opposite to the windingdirection of the pipe member 11 at an angle which is larger than 90°.

In the case of the schematically outlined embodiment of the yarn storageand feed device F according to FIG. 1, the area of the yarn path betweenthe yarn guide member 10 and the storage surface 2 is a particularlycritical area in so far as it is more likely that yarn breaks will occurin this area than in the vicinity of the yarn guide surfaces L of theyarn guide bodies 8 and 13. This is due to the large deflection angles(180°-β, 180°-α, and contrary to the direction of winding) and theresultant frictional forces between the yarn and the yarn guide surfacesL.

In order to make the frictional resistance in this critical area low andin order to treat the yarn Y as gently as possible, at least the yarnguide surface L in the yarn guide member 12 is made of a high-densitysintered ceramic material containing one or several carbide, nitride orcarbonitride hard materials of the following group of elements: Si, B,Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, as a main component, preferablysilicon nitride whose surface has optimum sliding properties for yarnsof every quality (synthetical as well as natural ones). It will besufficient when the yarn guide surface L is provided with a coating orcovering of this high-density sintered material. It will, however, beexpedient when the yarn guide member 12 as a whole consists of a formedpart which is made of this high-density sintered material and which isproduced by isostatic hot-pressing in a capsule. The isostatichot-pressing can also be carried out in a suitable moulding cavitywithout using any capsule.

In view of the fact that the yarn, when running along its yarn path, isalso deflected on the other yarn guide surfaces and rubs against saidsurfaces, it will be expedient when also the other yarn guide surfaces,at least those having a major deflection angle, are made of the samehigh-density sintered material containing e.g. silicon nitride as a maincomponent. The same applies to the draw-off edge 4 of the storage memberS where a coating or an insert ring 16 of high-density sintered materialis provided for forming the yarn guide surface L across which the yarnslides upon being removed and deflected towards the axis 5. In the caseof this embodiment, the storage member S standstill, whereas the windingmember M rotates. It is, however, also imaginable to select an operatingprinciple which functions the other way round and in the case of whichthe winding member stands still, whereas the storage member S rotates.Due to the structural design employed, a yarn guide surface L close toor at the draw-off side A will then often be the yarn guide surfacewhich is critical with regard to yarn breaks and which has a largerdeflection angle.

On the basis of FIG. 2, a yarn storage and feed device F is describedwhich is suitable for being used in practice and which operates inaccordance with the above-mentioned functional principle of FIG. 1.Corresponding components are provided with the reference numerals whichhave been used in FIG. 1.

The housing 7, in which the main shaft 9 as well as the storage member Sare rotatably supported, is secured to a support member, which is notshown, with the aid of a holding means 14. The housing 7 has providedtherein a drive motor 15 for the main shaft 9 plus the pipe member 11.Furthermore, magnets 17 are distributed within the housing, said magnets17 being in alignment with magnets 18 connected to the storage member S,which is, in principle, adapted to be rotated on the main shaft 9, andmaintaining the storage member S in a stationary condition when the mainshaft 9 rotates. A winding cone 19, which is connected to the main shaft9, extends between the magnets 17 and 18, said winding cone 19 havingattached thereto the pipe member 11 in the free end of which the yarnguide member 12 including the guide surface L, which has here thelargest deflection angle (180°-α), is provided in such a way that theyarn moving out of the pipe member 11 in an oblique radial direction isplaced substantially tangentially onto the storage surface 2 of thestorage member S in a direction opposite to the winding direction. Thestorage member S comprises two interengaging rod cage halves 20a and20b, the axis of rotation of the rod cage half 20b being in alignmentwith the axis 5, whereas the axis of rotation of the rod cage half 20ais arranged such that it is eccentric and inclined relative to the axis5 so as to generate an advance movement for the yarn windings in theyarn supply, which is not shown. In the interior of the storage memberS, a filler 21 is provided, which prevents an ingress of contaminations.

The draw-off edge 4 of the storage member S has associated therewith abrake ring 22 forming with elastic members--in a known manner--aretardation means for the yarn take-off point which circulates duringthe yarn take-off process. The housing 7 has provided thereon thelongitudinally extending holding means 6 for the yarn guide member 13,said holding means 6 having additionally provided therein a sensor means23 used for monitoring the size of the yarn supply.

The yarn guide member 8 is preceded by a supplementary unit V containingan additional yarn guide surface L on its inlet side. The supplementaryunit can, for example, be a yarn motion monitoring device or a feelerunit. The yarn guide member 10 is accommodated within the hollow mainshaft 9 and connects the passage in said main shaft 9 with the pipemember 11. In the case of this embodiment, the highest degree ofdeflection along the yarn path occurs within the yarn guide member 12along the yarn guide surface L, in accordance with FIG. 1. In the caseof other embodiments, however, the strongest degree of deflection mayalso occur at a different yarn guide surface.

At least the yarn guide surface L within the yarn guide body 12 is madeof high-density sintered material containing e.g. silicon nitride as amain component. However, also the other yarn guide surfaces L providedalong the yarn path may consist of the same material.

FIGS. 3a and 3b show a special embodiment of the yarn guide member 12 ofFIGS. 1 and 2 more clearly. The yarn guide member 12, which consists ofa high-density sintered material containing e.g. silicon nitride as themain component, is provided with a sleevelike basic body 24 having acontinuous passage 28 with inner walls 25. A straight wall portion 26extends at the upper side of the passage 28, this being the locationwhere contact with the yarn will normally hardly occur. At the lowerside of the passage 28, the yarn guide surface L, which shows acontinuous uniform curvature, is formed as a convex groove 30, whichstarts, with comparatively narrow dimensions, at a shoulder 29 and whichis provided with rounded flanks 31 on its sides. After the highest pointof the yarn guide surface L, said yarn guide surface descends outwardsuntil it finally ends in an oblique collar 27 circumferentiallyextending at least along part of the periphery of the basic body 24. Thepassage end section facing the collar 27 widens in a funnel-shapedmanner and defines a trough 32 (whose limits are indicated by the brokenline) so as to guarantee easy yarn withdrawal in a direction opposite tothe winding direction, this yarn withdrawal being guaranteedindependently of the direction of rotation of the main shaft 9. Theoblique end face of the collar 27 is provided with reference numeral 34,whereas the rear end face, which extends at right angles to the axis ofthe sleevelike basic body 24, is provided with reference numeral 33. Theouter periphery of the basic body 24 is provided with a cylindricalportion 36 so that the yarn guide body 12 can be inserted in the pipemember 11. The back of the collar 27 defines an insertion limiting means37. The yarn guide member 12 can be secured in position in the pipemember by means of a press fit. It would, however, also be possible tofasten said yarn guide member 12 with glue or with the aid of lockingmeans. An important point is that the yarn (indicated by thedot-and-dash line) runs onto and away from the yarn guide surface L inan approximately tangential direction at the starting section and at theend section of said yarn guide surface L and that the radius ofcurvature of said yarn guide surface remains substantially the samethroughout the yarn guide surface length so as to make the frictionalforces to which the yarn is subjected uniform.

The yarn guide member 12 is a formed part made of a high-densitysintered material containing e.g. silicon nitride as the main component.Optionally, the sintered material additionally contains between 1% byvolume and 8% by volume, preferably approx. 2.5%, of boron nitrideand/or boron carbide and/or yttrium oxide as an additive. The yarn guidemember 12 is in this form produced by isostatic hot-press sintering in amould cavity or in an encapsulation, e.g. a glass encapsulation; in saidglass encapsulation, a preform consisting of ceramic raw material iscovered with a boron carbide or a boron nitride layer so as to preventundesirable glass components or other components from penetrating intothe preform. Normally, a suspension of silicon nitride powder is firstformed for eliminating coarser grains so that only grain sizes ofapprox. 1 micron will remain in the preform, said grain sizes being, inthe final analysis, one of the factors which are responsible for thehigh density and the smoothness of the finished product. The preform isformed, under moderate pressure and at a low temperature, from the massof small silicon nitride grains, which can have added theretoconventional additives for sintered ceramic material, the dimensions ofsaid preform being still slightly larger than the final dimensions ofthe yarn guide body 12. The thus compacted preform is then inserted e.g.in the above-mentioned glass encapsulation and pressure is appliedthereto, said pressure being maintained constant throughout thehot-press sintering process. Subsequently, a high temperature is appliedduring a period of time of considerable length for the purpose ofsintering, and then the encapsulation is removed and the surface iscleaned so as to remove residues of the capsule. The yarn guide member12 is now ready for use.

A yarn guide member 12 according to FIGS. 3a, 3b was used for testscarried out for the purpose of determining the static frictional forceand the coefficient of friction for two types of yarns.

EXAMPLE 1

The angle β (FIG. 1) was 45°, whereas the deflection angle was(180°-α)=157° or the angle was 23°. The value measured was the ratiobetween F1 and F2, this ratio being equal to the value e^(u). The forceF1 occurred in the yarn between the yarn guide member 12 and the storagesurface 2. The force F2 occurred in the yarn between the yarn guidemember 10 and the yarn guide member 12. Conventional sintered ceramicmaterial of the type hitherto used for yarn guide surfaces resulted in avalue of 1.88 for F1:F2 in the case of a yarn having a conventional yarnnumber, whereas the same yarn guide surface L made of high-densitysintered material, which contained silicon nitride as a main componentand approx. 2.5% boron carbide or yttrium oxide, resulted in a value of1.64. This means an improvement by approx. 12.7%.

In the case of a synthetic filament yarn having a conventional yarnnumber, a value of 2.21 was obtained when the customary ceramic materialwas used, whereas the same guide surface made of the above-mentionedhigh-density sintered material resulted in a value of 1.98 for the sameyarn. This means an improvement by approx. 10.4%.

EXAMPLE 2

In the case of an angle β of 60° and a deflection angle of 177° (α=13°),a value of 2.04 was obtained when a guide surface of conventionalsintered ceramic material was used for a cotton yarn having aconventional yarn number, whereas the use of the same yarn on the sameguide surface, which consisted of high-density sintered materialcontaining silicon nitride as the main component and approx. 2.5% byvolume of boron carbide or yttrium oxide, resulted in a value of 1.75.This means an improvement by approx. 14.2%.

Under the same conditions, a value of 2.45 was obtained in the case of asynthetic filament yarn having a conventional yarn number, whereas thehigh-density sintered material resulted in a value of 2.17. This meansan improvement by approx. 11.4%.

EXAMPLE 3 Determination of the Coefficient of Friction

In order to determine the coefficient of friction, the test was carriedout with a yarn length of 2×20 cm and a load of approx. 30 cN, and theyarn guide member as well as the yarn used for the test were cleanedwith alcohol after each test cycle. A PES yarn, i.e. a polyester ornylon yarn, and a cotton yarn were used for the test; each of said yarnswas drawn across the yarn guide surface under load at a first speed of100 mm/min and, subsequently, at a second speed of 1000 mm/min.

Three test cycles were carried out at each speed and with each yarn.

In the course of these tests, the coefficient of friction obtained forthe cotton yarn showed the tendency to decrease slightly with eachpassing test cycle, whereas the coefficient of friction obtained for thePES yarn increased slightly with each passing test cycle.

The following individual average values were ascertained on the basis ofthe three test cycles which were carried out respectively:

    ______________________________________                                                 HD-SiN   convent. sintered                                                    sintered material (type 1)                                                                           convent. sintered                             PES      material (Al.sub.2 O.sub.3)                                                                          material (type 2)                             ______________________________________                                         100 mm/min                                                                            0.263    0.292         0.292                                         1000 mm/min                                                                            0.246    0.286         0.270                                         cotton                                                                         100 mm/min                                                                            0.148    0.235         0.205                                         1000 mm/min                                                                            0.175    0.235         0.230                                         ______________________________________                                    

These tests show clearly that, in spite of the extreme deflection anglechosen for the tests, the yarn is mechanically treated much more gentlyby yarn guide surfaces made of sintered material, which contain siliconnitride as the main component, than it would be treated on yarn guidesurfaces consisting of conventional sintered material. This gentletreatment of the yarn results in a reduction of the yarn breaks whichhave hitherto taken place predominantly in the yarn path area in whichthe highest degree of deflection and, consequently, the strongestmechanical load on the yarn existed. This applies to all yarn numbersand to all qualities of yarns which are processed by such yarn storageand feed devices.

Moreover, the mechanical abrasion resistance of the high-densitysintered material containing silicon nitride as the main componentguarantees a long service life without any perceivable wear even in thecase of specially abrasive yarns and the high mechanical strength of thesintered material provides the possibility of constructing the yarnguide members such that they are very gracile and light, and this willresult in desirably small moving masses in particular in the case of theyarn guide member provided within the winding member. An additional,positive aspect of the high-density sintered material is that the yarnguide surfaces contribute to a uniform yarn take-off tension which is assmall as possible, such a yarn take-off tension being advantageous inconnection with modern textile machines.

We claim:
 1. In a yarn storage and feed device for a textile machine,said device having a feed side, a take-off side and a storage bodydisposed between said feed side and said take-off side, said storagebody having a storage surface for storing a length of yarn, a windingmember for winding the yarn on said storage surface, means supportingsaid winding member and said storage body for relative rotation fortransporting the yarn through a yarn path extending from said feed sideto said storage surface and thence extending from said storage surfaceto said take-off side, yarn guide members having yarn guide surfacesdisposed along said yarn path for slidable engaging and guiding themovement of the yarn, at least one of said yarn guide surfaces beingeffective for changing the direction of travel of the yarn through alarge deflection angle, the improvement which comprises: said one yarnguide surface is formed of a high-density, sintered molding of hardceramic material, said molding having been made by isostatic hotpressing in an encapsulation, said one yarn guide surface exhibiting lowfriction to yarn moving thereacross and being effective to minimize yarnbreaks.
 2. A yarn storage and feed device according to claim 1, whereinsaid sintered molding contains, as a main component, at least one hardceramic material which is a ceramic compound of an element selected fromthe group consisting of:Si, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.
 3. Ayarn storage and feed device according to claim 1, wherein said one yarnguide surface has a deflection angle exceeding 90°.
 4. A yarn storageand feed device according to claim 1, wherein said sintered moldingcontains, as a main component, at least one ceramic compound selectedfrom the group consisting of the nitrides, carbides and carbonitridesofSi, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.
 5. A yarn storage and feeddevice according to claim 1, wherein said high-density sintered molding,which forms said one guide surface, consists essentially of from 1% byvolume to 8% by volume of an additive selected from the group consistingof boron nitride, boron carbide, yttrium oxide and mixtures thereof, andthe balance is silicon nitride.
 6. A yarn storage and feed deviceaccording to claim 1, in which at least one additional yarn guidesurface along the guide path is formed of a second high-density sinteredmolding of hard ceramic material made by hot isostatic pressing in anencapsulation.
 7. A yarn storage and feed device according to claim 6,wherein said sintered moldings contain, as a main component, at leastone hard ceramic material which is a ceramic compound of an elementselected from the group consisting of:Si, B, Ti, Zr, Hf, V, Nb, Ta, Cr,Mo and W.
 8. A yarn storage and feed device according to claim 6,wherein said sintered moldings contain, as a main component, at leastone ceramic compound selected from the group consisting of the nitrides,carbides and carbonitrides ofSi, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.9. A yarn storage and feed device according to claim 1, wherein saidstorage body has a cylindrical shape and comprises a yarn draw-off edgeserving as a yarn guide surface, and wherein said yarn guide surface ofsaid draw-off edge is made of a high-density hard sintered material madeby hot isostatic pressing in an encapsulation.
 10. A yarn storage andfeed device according to claim 9, wherein said yarn guide surface ofsaid draw-off edge is made of a high-density sintered molding andcontains, as a main component, at least one or several hard ceramicmaterial which is a ceramic compound of an element selected from thefollowing group:Si, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.
 11. A yarnstorage and feed device according to claim 9, wherein said yarn guidesurface of said draw-off edge is made of a high-density sinteredmaterial which contains, as a main component, at least one ceramiccompound selected from the group consisting of the nitrides, carbidesand carbonitrides ofSi, B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.
 12. Ayarn storage and feed device according to claim 1, wherein said storagebody is stationary and said winding member is a pipe member, a hollowmain shaft from which said pipe member extends, a rotary drive meansconnected for rotating said main shaft, said pipe member extendingapproximately radially outwards up to and beyond the storage surface ofsaid storage body, the free end of said pipe member having providedtherein a yarn guide member including a guide surface which defines adeflection angle exceeding 90° for the yarn moving out of said mainshaft and towards said storage surface, wherein said yarn guide memberof said pipe member is a high-density sintered molding having aninternal passage, said yarn guide surface of said pipe member is formedon the wall of said passage as a convex groove whose starting and endsections are approximately in alignment with the direction in which theyarn moves toward and away from said yarn guide member of said pipemember.
 13. A yarn storage and feed device according to claim 12,wherein the curvature of said groove, when seen in a longitudinalsection through said yarn guide member of said pipe member, has auniform radius of curvature throughout the deflection angle.
 14. A yarnstorage and feed device according to claim 12, wherein the end sectionof said groove is a funnel-shaped trough which, when seen relative tothe centre of the passage, extends over approximately 160° (radianmeasure).
 15. A yarn storage and feed device according to claim 12,wherein said yarn guide member of said pipe member is constructed as asleeve having a cylindrical outer portion and a collar inclined relativeto the axis of said outer portion, which collar as a border of thetrough projects outwards at least over part of the periphery of thecylindrical portion and defines an insertion limiting means for the yarnguide member of said pipe member.
 16. A yarn storage and feed deviceaccording to claim 1 in which said high-density sintered molding, whichforms said one guide surface, consists essentially of about 2.5% byvolume of an additive selected from the group consisting of boronnitride, boron carbide, yttrium oxide and mixtures thereof, and thebalance is silicon nitride having a particle size of about 1 micron.